The Office of Management and Budget led a required call with agency officials last week.

As lawmakers and the president hurtle toward a Dec. 21 deadline to approve a spending package for federal agencies that have not yet received funding for the 2019 fiscal year, those agencies have begun to prepare for the possibility of a shutdown.

Congress has until Friday to approve a bill to fund the departments of Transportation, Housing and Urban Development, State, Interior, Agriculture, Treasury, Commerce, Homeland Security and Justice, as well as other independent agencies. Otherwise, most of those entities will be forced to shut down some or all of their operations and furlough at least some employees, depending on how those operations are funded, their role in national security and public safety, and other factors.

On Friday, the Office of Management and Budget warned agency leaders in a phone call that they should begin to prepare for a lapse in appropriations. The conversation is routine any time a funding deadline nears.

“Per guidance . . . one week prior to the expiration of appropriations, OMB communicates with senior agency officials to remind them of their responsibilities to review and update their lapse plans and to take other necessary steps to prepare for a potential lapse in appropriations, regardless of whether the enactment of appropriations appears imminent,” said an senior administration official.

The primary sticking point in negotiations is how much money should go toward border security and to President Trump’s proposed wall along the U.S.-Mexico border. Democrats initially floated $1.3 billion in general border security funding, but in recent days they have pressed for a full-year continuing resolution for the Homeland Security Department, which would reallocate last year’s funding for fencing and other initiatives elsewhere.

Trump, for his part, has insisted on $5 billion specifically for the wall, in addition to broader border security provisions. Last week, the president insisted he would be “proud” to shut down federal agencies over the issue.

According to an analysis by Government Executive, of the 850,000 civilian employees at unfunded agencies, about 41 percent, or 345,000, would be subject to furloughs if lawmakers miss the Dec. 21 deadline. While some agencies, like the National Science Foundation, would see the vast majority of their workforces furloughed, others, such as the Environmental Protection Agency, could see as little as 1.8 percent of employees sent home.

That is in part due to a 2017 change in shutdown guidance from OMB, which encouraged departments and agencies to use “carry-forward funding” and “transfer authority” to mitigate the potential impact of a lapse in appropriations.